Lifting device including telescoping mast

ABSTRACT

A lifting device for elevating a load includes a telescoping mast having an inner mast section telescopically received within an outer mast section and configured to extend in an upward direction and retract in a downward direction relative to the outer mast section. An emergency brake is secured to the inner mast section and includes first and second eccentrics configured to rotate relative to the inner mast section between an unlocked position, in which the first and second eccentrics are free from locking engagement with the outer mast section to allow retraction of the inner mast section, and a locked position, in which the first and second eccentrics are in locking engagement with the outer mast section to inhibit retraction of the inner mast section. A base of the lifting device may include a holder having a tapering interior for receiving the telescoping mast.

FIELD OF THE INVENTION

The present invention generally relates to a lifting device including a telescoping mast.

BACKGROUND

In general, a lifting device including a telescoping mast may be used to elevate a load. As examples, lifting devices including telescoping masts may be configured to elevate communication devices (e.g., antennas), lighting, vehicles (e.g., cars), vehicle components (e.g., transmissions), constructions panels (e.g., drywall, plywood panels, fiberboard panels, etc.), and other loads.

There is a possibility that these lifting devices may fail in use, whereby the telescoping mast will unexpectedly and rapidly collapse, and the load will drop under the collapsing telescoping mast. For example, panel hoists or lifts are lifting devices used to elevate a construction panel into position. Panel lifts are generally comprised of a telescoping mast and a winch. The winch usually has a braking system to prevent the telescoping mast from collapsing under the weight of the panel. However, should the line associated with the winch break or otherwise fail, the braking system will be unable to prevent the telescoping mast from collapsing under the weight of the panel. This can result in the load falling off the lifting device or the lifting device tipping over potentially causing damage or injury.

In addition, the lifting device may include a base. The base may have an opening for removably receiving the telescoping mast to connect the two components to one another. However, the tolerances required to allow the telescoping mast to be detachable from the base often results in the telescoping mast being susceptible to horizontal movement or wiggle when detachably secured to the base. While this movement can be minor close to the base, when the telescoping mast is fully extended, any horizontal movement is magnified at the top of the telescoping mast, which can damage the lifting device and/or result in the load falling off the lifting device or the lifting device tipping over potentially causing damage or injury.

SUMMARY

In one aspect, a lifting device for elevating a load is disclosed. The lifting device includes a telescoping mast and a brake. The telescoping mast has opposite upper and lower ends. The telescoping mast includes an outer mast section and an inner mast section telescopically received within the outer mast section. The inner mast section is configured to extend in an upward direction and retract in a downward direction relative to the outer mast section. The emergency brake is secured to the inner mast section. The emergency brake includes first and second eccentrics that are configured to rotate relative to the inner mast section between an unlocked position, in which the first and second eccentrics are free from locking engagement with the outer mast section to allow retraction of the inner mast section within the outer mast section, and a locked position, in which the first and second eccentrics are in locking engagement with the outer mast section to inhibit retraction of the inner mast section within the outer mast section.

In another aspect, a lifting device for elevating a load is disclosed. The lifting device includes a telescoping mast, a head piece and a movable base. The telescoping mast is configured to extend and retract in a heightwise direction and has opposite upper and lower ends. The head piece is secured to the telescoping mast at the upper end thereof and configured to support the load thereon. The movable base is configured to support the telescoping mast in an upright position. The base includes a mast holder sized and shaped to receive a lower end of the telescoping mast therein. The mast holder defines an opening at an upper end thereof and through which the lower end of the telescoping mast enters the mast holder. The mast holder includes opposing interior mast holder surfaces that are configured to engage the lower end of the telescoping mast when the telescoping mast is received in the mast holder. The opposing interior holder surfaces define a transverse distance therebetween that tapers in a downward direction away from the opening.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of a panel lift constructed according to the teachings of the present disclosure;

FIG. 2 is a right elevational view of the panel lift;

FIG. 3 is an enlarged detail view of a telescoping mast of the panel lift as indicated in FIG. 2, with a portion of the telescoping mast shown in broken-out section to expose a first embodiment of an emergency brake in an unlocked position;

FIG. 4 is an enlarged detail view of the telescoping mast of the panel lift as indicated in FIG. 2, with a portion of the telescoping mast shown in broken-out section to expose a second embodiment of an emergency brake in an unlocked position;

FIG. 5 is similar to FIG. 3, with the emergency brake in a locked position;

FIG. 6 is similar to FIG. 4, with the emergency brake in a locked position;

FIG. 7 is an enlarged detail view of the telescoping mast supported by a base as indicated in FIG. 2;

FIG. 8 is a front elevational view of the panel lift;

FIG. 9 is an enlarged, detail view of the telescoping mast supported by the base as indicated in FIG. 8;

FIG. 10 is an enlarged, exploded perspective view of the base;

FIG. 11 is an enlarged perspective view of the first embodiment of the emergency brake;

FIG. 12 is a front elevational view of FIG. 11;

FIG. 13 is an enlarged perspective view of the second embodiment of the emergency brake;

FIG. 14 is a front elevational view of FIG. 13;

FIG. 15 is an enlarged perspective view of a head piece of the panel lift; and

FIG. 16 is an enlarged perspective view of a mounting assembly of the head piece.

Corresponding reference characters indicate corresponding parts throughout the drawings.

DETAILED DESCRIPTION

Referring to FIG. 1, a lifting device for elevating a load constructed according to the teachings of the present disclosure is generally indicated at reference numeral 10. In the illustrated embodiment, the lifting device 10 is constructed as a panel lift for elevating a construction panel. It is understood that in other embodiments, the lifting device 10 may be configured as a different type of lifting device for elevating other loads, including but not limited to communication devices (e.g., antennas), lighting, vehicles (e.g., cars), vehicle components (e.g., transmissions), and other loads.

The lift 10 generally includes a base 20, a telescoping mast 40, and a head piece 80, each of which is indicated generally in FIG. 1. The base 20 receives a lower end of the telescoping mast 40 and supports the telescoping mast in an upright position. The head piece 80 is mounted on an upper end of the telescoping mast 40. As will be described in more detail below, the base 20, the telescoping mast 40, and the head piece 80 are detachable from one another.

Referring to FIGS. 1, 7, 9, and 10, the base 20 includes a mast holder, generally indicated at 21, having a top plate 22, a bottom plate 23, and side plates 24 extending from the top plate 22 to the bottom plate 23 to connect the top and bottom plates. As shown best in FIG. 1, the base 20 also includes three legs 25 secured to the mast holder 21 and extending outward therefrom. A caster 26 secured to each leg 25 supports the base 20 and allows the base to be rolled or moved over a surface, such as a floor. In the illustrated embodiment, one leg 25 is rigidly secured to the mast holder 21 between the top plate 22 and the bottom plate 23, and the other two legs are pivotably secured to the mast holder between the top plate and the bottom plate via respective fasteners, e.g., bolts 27, to allow these two legs to selectively rotate between deployed and stored configurations. The base 20 may be of other designs and constructions without necessarily departing from the scope of the present invention.

As can be seen best from FIG. 10, locking pins 29 extend through the respective pivotably secured legs 25. Each locking pin 29 is removably insertable into one of two positioning holes 31 on the bottom plate 23 to lock the leg 25 in a selected position and prevent rotation relative to the mast holder 21. In the deployed configuration, the locking pins 29 are received in the respective positioning holes 31 corresponding to the deployed configuration, and likewise, in the stored configuration (not shown), the locking pins are received in the respective positioning holes 31 corresponding to the stored configuration. In the deployed configuration, each leg 25 extends from the mast holder 21 in a spaced apart, tripod arrangement. In the stored configuration, each of the pivotably secured legs 25 extends alongside and in the same general direction as the rigidly secured leg 25 to reduce the overall footprint of the base 20 for easier transportation and storage. The locking pins 29 can be biased with a spring (not shown) toward the bottom plate 23.

In the illustrated embodiment, a foot 32 is pivotably attached to the mast holder 21 to prevent the base 20 from rolling when the panel lift 10 is in use. When in use, the foot 32 is rotated down to engage the floor to resist movement. When not in use, the foot 32 is rotated upward and clipped to one of the legs 25 for storage. The end of the foot 32 can include a rubber grip 33 to better engage the floor and provide greater resistance to movement.

The mast holder 21 is configured to support the telescoping mast 40 in an upright position. The top plate 22 defines an upper opening 34, and the bottom plate 23 defines a lower opening 35. The upper and lower openings 34, 35 are sized and shaped to receive the telescoping mast 40 therein. In the illustrated embodiment, the upper and lower openings 34 and 35 are rectangular to match the rectangular shape of the telescoping mast 40. It is to be understood that the upper and lower openings 34, 35 may be other shapes, such as circular, corresponding to other cross-sectional shapes of the telescoping mast without necessarily departing from the scope of the present invention. The upper opening 34 is sized to tightly receive the telescoping mast 40 to provide a first point of support against horizontal movement. In a preferred embodiment, the open area of the upper opening 34 is slightly greater than the cross-sectional area of the telescoping mast 40, and preferably no greater than necessary to receive the telescoping mast therein. The open area of the lower opening 35 is greater than the open area of the upper opening 34. The open area of the lower opening 35 is sized to be more than slightly greater than the cross-sectional size of the telescoping mast 40, having an amount of clearance allowing the telescoping mast to easily pass therethrough. The larger lower opening 35 allows the telescoping mast 40 to be more easily inserted into the mast holder 21, and avoids alignment problems when inserting the mast 40 into the openings 34, 35.

A support frame, including frame members 36, is attached to and extends below the bottom plate 23. In the illustrated embodiment, the frame members 36 include cross-wise, U-shaped frame members (e.g., vertical, cross-wise plates). It is understood that the frame and the frame members 36 may be of other designs and configurations, including interconnected panel frame members. The frame members 36 have interior holder surfaces 37 extending downward from the bottom plate 23, and defining a seat 38 generally opposing the lower opening 35. The interior holder surfaces 37 extend inward or toward a vertical imaginary axis passing through the centers of the upper and lower openings 34, 35 from adjacent the bottom plate 23 toward the seat 38. In the illustrated embodiment, the upper and lower openings 34, 35 are square shaped and the interior holder surfaces 37 are positioned on each side of the lower opening 35. As shown in FIGS. 7 and 9, each pair of opposing interior holder surfaces 37 (e.g., two pairs as illustrated) defines a transverse distance therebetween that tapers in a downward direction. Thus, the effective open cross-sectional area of the support frame defined by the frame members 36 tapers in a downward direction, such that the effective open cross-sectional area of the support frame adjacent the bottom plate 23 is greater than the cross-sectional area of the support frame adjacent the seat 38. In the illustrated embodiment, the cross-sectional area of the support frame adjacent to the seat 38 is equal to the cross-sectional area of lower end of the telescoping mast 40.

As shown in FIGS. 7-10, the upper opening 34, the lower opening 35, and the interior holder surfaces 37 are axially aligned such that when the telescoping mast 40 is inserted into the base 20, the telescoping mast is received in the upper opening, upper opening and between the interior holder surfaces. The engagement of the interior holder surfaces 37 with the lower end of the telescoping mast 40 wedges the lower end of the telescoping mast in the frame and provides a second point of support against horizontal movement. The combination of upper opening 34 and the interior holder surfaces 37 provides two points of support, spaced apart vertically from one another along the telescoping mast 40, against horizontal movement. Having two points of support spaced apart vertically from one another increases the ability of the base 20 to inhibit horizontal movement or wiggle in the telescoping mast 40. Because the upper opening 34 and the interior holder surfaces 37 engage the telescoping mast 40 on multiple sides, the telescoping mast is supported against horizontal movement in any horizontal direction. The interior holder surfaces 37 may taper inward an amount such that the telescoping mast 40 engages the interior holder surfaces before reaching the seat 38 when the telescoping mast is inserted into the mast holder 21. Thus, the seat 38 may not directly support the lower end of the telescoping mast 38. However, the seat 38 will support the telescoping mast 40 if the lower end of the telescoping mast 38 does not adequately engage the interior holder surfaces 37 above the seat. Preferably, the lower end of the telescoping mast 38 adequately engages (i.e., is wedged by) the interior holder surfaces 37 immediately adjacent the seat 38 so that the interior holder surfaces inhibit horizontal movement or wiggle in the telescoping mast 40 and the lower end of the telescoping mast rests on the seat. However, because of the tapering interior holder surfaces 37, the mast holder 21 will adequately support the telescoping mast 40 and inhibit horizontal movement within dimensional tolerances of the lower end of the mast holder and/or the mast holder.

Referring to FIGS. 1, 2 and 8, the telescoping mast 40 includes an outer mast section 41, an inner mast section 42, and a second inner mast section 43. The second inner mast section 43 is telescopically received within the inner mast section 42, and the inner mast section is telescopically received within the outer mast section 41. The second inner mast section 43 slides in and out of the upper end of the inner mast section 42. The inner mast section 42 slides in and out of the upper end of the outer mast section 41. Plastic guides (not shown) may be placed in the inner and outer mast sections 42, 41 allow the second inner and inner mast sections 43, 42 to telescope smoothly and reduce horizontal movement in the inner and outer mast sections, respectively. The upper end of the second inner mast 43 section may have a cylindrical opening (not shown) to attach the head piece 80 to the telescoping mast 40, as described in more detail below.

A prime mover, generally indicated at 44, is configured to extend and retract the telescoping mast 40. The winch 44 is connected to the outer mast section 41 via an arm 39 and can rotate between a stored position (not shown) in which the winch is positioned alongside the outer mast section and a deployed position in which the winch is angled away from the outer mast section. A locking pin 45 engages an opening 47 on the support bracket 46 to lock the winch 44 in place. The locking pin 45 can be biased in a locked configuration with a spring. The winch 44 includes a spool 48 and crank 50 connected to the spool. A line 49 is operatively connected to (i.e., wound on) the spool 48 of the winch 44. It is understood the line 49 can be any flexible connection member such as a cable, strap, rope or chain without departing from the scope of the present disclosure. The illustrated crank 50 is in the form of handle or wheel secured to the spool 48 to allow an operator to wind or unwind the line 49. The winch 44 includes a spring loaded handbrake or winch brake 51 to prevent the line 49 from unwinding. One end of the line 49 is wrapped around the spool 48 with the other end attached to the second inner mast section 43, and the line 49 engaging a series of pulleys 52 (FIGS. 3-6) therebetween, as is generally known in the art. The pulleys 52 are located at the upper end of the outer mast section 41, the lower and upper end of the inner mast section 42 and the lower end of the second inner mast section 43. The line 49 engages the pulleys 52 in that order as it travels from the winch 44. Rotating the winch 44 selectively extends and retracts the telescoping mast 40 in upward and downward directions, respectively (i.e., in a heightwise direction). As the operator winds the line 49 with the winch 44, the distance the line travels between the pulley 52 located at the upper end of the outer mast section 41 and the pulley located at the lower end of the inner mast section 42 is reduced, extending the inner mast section in an upward direction out of the outer mast section. At the same time, the distance the line 49 travels between the pulley 52 located at the upper end of the inner mast section 42 and the pulley located at the lower end of the second inner mast section 43 is reduced, extending the second inner mast section in an upward direction out of the inner mast section. As the operator unwinds the line 49 with the winch 44, the distance the line travels between the pulley 52 located at the upper end of the outer mast section 41 and the pulley located at the lower end of the inner mast section 42 is increased, retracting the inner mast section in a downward direction into the outer mast section. At the same time, the distance the line 49 travels between the pulley 52 located at the upper end of the inner mast section 42 and the pulley located at the lower end of the second inner mast section 43 is increased, retracting the second inner mast section in a downward direction into the inner mast section. Thus, the operator can extend the telescoping mast 40 in an upward direction and retract the telescoping mast in a downward direction by operating the winch 44. Other embodiments may include other ways of extending and retracting the telescoping mast 40, such as through pneumatic, electric, or hydraulic prime movers.

As shown in FIGS. 2-4, a first embodiment of a fall prevention device or an emergency brake, generally indicated at 100, is included on the inner mast section 42, and a second embodiment of an emergency brake, generally indicated at 200, is included on second inner mast section 43. As explained in more detail below, the emergency brakes 100, 200 prevent the inner mast section 42 and second inner mast section 43, respectively, from collapsing at a high rate of acceleration should the line 49 break or if the winch brake 51 is released without controlling the descent with the winch. It is understood that the two different embodiments are shown in the single panel lift 10 for illustrative purposes and the panel lift may have the same embodiment for each of its emergency brakes.

As shown in FIGS. 3, 5, 11 and 12, the first emergency brake 100 includes first and second eccentrics 110, 120 rotatably mounted on a shaft 130. Each eccentric 110, 120 can rotate independent of the other. The eccentrics 110, 120 include respective eccentric bushings or bearings 118 to reduce the friction between each eccentric 110, 120 and the shaft 130, allowing each eccentric to more freely rotate. The shaft 130 extends through the bearings 118 at first end portions of the eccentrics 110, 120. Second end portions opposite the first end portions of the eccentrics 110, 120 include an engagement edge or surface 116. The engagement surface 116 contacts the telescoping mast 40 to engage the emergency brake 100. The engagement surface 116 may define a friction-enhancing structure 114. As described in more detail below, the friction-enhancing structure 114 engages the telescoping mast 40 to facilitate the frictional engagement with the emergency brake 100. In the illustrated embodiment, the friction-enhancing structure 114 is a plurality of teeth located on each eccentric 110, 120 at the second end portions thereof. The engagement surface 116 may define other friction-enhancing structures, including but not limited to knurls, ribs, grooves, bumps, projections, etc., that enhance frictional engagement with the telescoping mast.

In the illustrated embodiment, each eccentric 110, 120 has a non-uniform radial distance between the axis of rotation of eccentric and engagement surface along the arc length of the engagement surface 116. More specifically, the radial distance between the axis of rotation of the eccentric 110, 120 and the lower end of the engagement surface 116 is greater than the radial distance between the axis of the rotation of the eccentric and the upper end of the engagement surface 116. Thus, as described in more detail below, as each eccentric 110, 120 rotates, the engagement surface 116 will move closer and eventually engage the telescoping mast 40. In the illustrated embodiment, the engagement surface 116 is arc shaped and may have a uniform radius of curvature along its arc length. However, in other embodiments, the engagement surface may have other shapes.

The illustrated emergency brake 100 also includes a torsion spring 140 disposed between the first and second eccentrics 110, 120 along the length of the shaft 130. The shaft 130 extend through a body of the torsion spring 140, and first and second legs of the torsion spring 140 are secured to the respective first and second eccentrics 110, 120 adjacent the engagement surface 116 (i.e., at or adjacent the second end portions). The spring 140 applies opposite spring forces to the eccentrics 110, 120, including a first spring force applied to the first eccentric and a second spring force applied to the second eccentric in a direction opposite the first spring force. Thus, the spring 140 rotates the first and second eccentrics 110, 120 in opposite directions. In the preferred embodiment, the ends of the spring 140 extend through openings 141 in each eccentric 110, 120. However, any suitable attachment method, such as welding or fasteners, is within the scope of the present invention. In other embodiments, the emergency brake 100 may include other ways of applying a biasing force (e.g., resiliently biasing force) to the eccentrics in directions toward the engagement positions. For example, one or more linear springs may be operatively connected to the eccentrics.

The emergency brake 100 is secured to the inner mast section 42 near the lower end thereof. The shaft 130 is attached to the inside of the inner mast section 42 and supports the first and second eccentrics 110, 120 inside the inner mast section. The inner mast section 42 includes first and second openings 61 and 62 corresponding to the first and second eccentrics 110, 120. The first and second openings 61 and 62 are positioned to allow the first and second eccentrics 110, 120 to rotate and extend through the first and second openings to engage the outer mast section 41. A stop 150 is secured to the inner mast section 42 above the emergency brake 100 to prevent the second inner mast section 43 from contacting the brake. The stop 150 can also prevent any over rotation of the first and second eccentrics 110, 120. In the illustrated embodiment, the stop 150 is a second shaft positioned above the shaft 130 of the emergency brake 100; however, any suitable device configured to prevent the second inner mast section from contacting the brake is within the scope of the present invention.

The emergency brake 100 prevents the inner mast section 42 from collapsing by frictionally engaging the outer mast section 41 in the event the inner mast section is subject to a sudden and uncontrollable collapse (e.g., free fall experienced if the line breaks or the telescoping mast's descent is not controlled with the winch 44). The first and second eccentrics 110, 120 each have a center of gravity spaced apart radially from its rotational axis (e.g., the shaft 130). At rest, gravity acting on the offset center of gravity and the reaction force applied at the first end portions of the eccentrics 110, 120 by the shaft 130 imparts a rotational force or torque to the eccentrics in a direction that tends to rotate the eccentrics toward one another about the shaft. In this unlocked position, shown in FIG. 3, the rotational forces of the first and second eccentrics 110, 120 compress the spring 140, storing potential energy. The spring 140 also prevents the first and second eccentrics 110, 120 from hanging completely below the shaft 130 (i.e., the first and second eccentrics are angularly offset relative to the rotational axis). In the unlocked position, the first and second eccentrics 110, 120 do not engage the outer mast section 41, however, the combination of the rotational forces due to gravity and the spring forces acting on the respective eccentrics 110, 120 positions each eccentric near the outer mast section 41. More specifically, the engagement surface 116 of the first and second eccentrics 110, 120 is situated near, but does not engage, the outer mast section 41, but is ready to engage the outer mast section upon a sudden and uncontrollable descent. The first and second eccentrics 110, 120 may or may not extend through the first and second openings 61 and 62 when in an unlocked position. Because the first and second eccentrics 110, 120 are free of locking engagement with the outer mast section 41 in an unlocked position, the eccentrics do not contact the outer mast section, the inner mast section 42 is free to retract within the outer mast section using the winch 44.

Upon a sudden and uncontrollable descent (e.g., free fall), such as when the line 49 breaks or the hand brake 51 is released without manually controlling the descent with the winch 44, the first and second eccentrics 110, 120 move or rotate into a locked position, shown in FIG. 5, in which the first and second eccentrics are in locking engagement with the outer mast section 41 to inhibit retraction of the inner mast section 42 within the outer mast section. When the inner mast section 42 is subject to a sudden and uncontrollable descent (e.g., free fall), the first and second eccentrics 110, 120 are no longer entirely supported by the shaft 130 (e.g., the first and second eccentrics are “weightless” in reference to the shaft), allowing the spring 140 to release its potential energy and rotate the first and second eccentrics outward and upward to engage or contact the outer mast section. In other words, the torque caused by gravity and the reaction force of the shaft 130 is decreased (theoretically, close to zero force) during sudden and uncontrollable descent (e.g., free fall) of the eccentrics 110, 120 and the shaft 130, and the spring force overcomes the force gravity acting on the eccentrics to impart a net force rotating the first and second eccentrics outward and upward to engage or contact the outer mast section.

The minimum magnitude of downward acceleration of the inner mast section 42 required to rotate the first and second eccentrics 110, 120 into the locked position is called the threshold magnitude. The threshold magnitude lies somewhere between greater than 0 ft/s² (no acceleration; at rest) and 32.2 ft/s² (9.81 m/s²; the acceleration due to gravity). If the inner mast section 42 accelerates downward at a magnitude below the threshold magnitude, the spring force is not able to overcome the torque acting on the eccentrics to rotate the first and second eccentrics 110, 120 into the locked position from the unlocked position and the first and second eccentrics remain free from locking engagement with the outer mast section 41. If the inner mast section 42 accelerates downward at a magnitude above the threshold magnitude, which will typically be the acceleration due to gravity during a sudden and uncontrollable decent or when the descent is not controlled with the winch (e.g., free fall), the spring force rotates the first and second eccentrics 110, 120 into the locked position, moving the first and second eccentrics into locking engagement with the outer mast section 41. The value of the threshold magnitude varies depending on, among other parameters, the mass of each eccentric 110, 120, the rotational friction between each eccentric and the shaft 130, and the spring constant k of the spring 140 (strength of the spring). The smaller the threshold magnitude, the quicker the emergency brake 100 will move into the locked position. However, it is preferred that the threshold magnitude is greater than a maximum magnitude of acceleration of the inner mast section 42 when the operator retracts the telescoping mast 40 with the winch 44, to prevent the emergency brake 100 from engaging the outer mast section 41 when the inner mast section is retracted. The emergency brake 100 will remain in the unlocked position as long as the magnitude of acceleration imparted by the operator when retracting the telescoping mast 40 is less than the threshold magnitude, allowing the inner mast section 42 to retract.

When the inner mast section 42 accelerates downward at a magnitude above the threshold magnitude, the spring force imparted by the spring 140 on the first and second eccentrics 110, 120 rotates each eccentric into locking engagement with the outer mast section. The first and second eccentrics 110, 120 rotate in opposite directions from the unlocked position to the locked position. As a result, the first and second eccentrics 110, 120 engage opposite sides of the outer mast section 41. As the spring 140 rotates each eccentric 110, 120 from the unlocked position, the engagement surface 116 on each eccentric engages the outer mast section 41. Once the engagement surface 116 of each eccentric 110, 120 start to engage the outer mast section 41, any continued downward movement of the inner mast section 42 relative to the outer mast section further secures the first and second eccentrics against the outer mast section. Once the engagement surface 116 starts to engage the outer mast section 41, the inner mast section 42 pushes down on the shaft 130 while the engagement surface of each eccentric remains engaged to the outer mast section, further rotating each eccentric. If the eccentrics 110, 120 include a friction-enhancing structure 114, such as teeth, the friction-enhancing structure engages the outer mast section 41 to facilitate the rotation of each eccentric 110, 120 by the outer mast section. Because the distance between the engagement surface 116 and axis of rotation of the shaft 130 increases, as each eccentric 110, 120 rotates, successive portions of the engagement surface 116 engage the outer mast section 41, increasing the locking force applied by each eccentric. At some point along the engagement surface 116, the engagement surface applies a sufficient amount of force against the outer mast section 41 to bring the inner mast section 42 to a stop (i.e. stop the inner mast section from moving relative to the outer mast section). The outer mast section 41 may or may not deflect as a result of the force applied by the eccentrics 110, 120. If the outer mast section 41 does deflect, the increasing distance along the engagement surface 116 will keep the engagement surface in contact with the outer mast section. Once the first and second eccentrics 110, 120 apply enough locking force against the outer mast section 41, the inner mast section 42 comes to a rest, stopping the fall of the inner mast section. In this locked position, the first eccentric 110 extends through the first opening 61 to engage the outer mast section 41 and the second eccentric 120 extends through the second opening 62 to engage the outer mast section, preventing the inner mast section 42 from falling relative to the outer mast section. Thus, it is apparent that the emergency brake 100 operates independent of the line 49 and is able to prevent the inner mast section 42 from falling should the line break or the descent is not controlled with the winch 44. Because the emergency brake 100 operates independent of the lifting or moving system that elongates or retracts the telescoping mast, the emergency brake 100 can be incorporated into any type of telescoping mast. For example, the emergency brake 100 can be incorporated into a telescoping lift, a panel lift, a drywall lift, a transmission lift, a lighting lift, a communications lift, or any other type of telescoping mast supporting a load that can be raised and/or lowered.

To disengage the emergency brake 100 from the locked position, the inner mast section 42 is extended or lifted in the upward direction. As the inner mast section 42 is lifted the first and second eccentrics 110, 120 rotate towards the unlocked position. This rotation gradually disengages the engagement surface 116 on each eccentric 110, 120 from contacting the outer mast section 41. Once each eccentric 110, 120 completely disengages the outer mast section 41, each eccentric rotates, due to gravity, back to the unlocked position. The inner mast section 42 can then be retracted or lowered in the downward direction.

Referring to FIGS. 4, 6, 13 and 14, a second embodiment of the emergency brake 200 is disclosed. The emergency brake 200 of the second embodiment is similar to the emergency brake 100 in the first embodiment and operates in a similar way. For ease of comprehension, where similar or identical parts are used, reference designators “100” units higher are employed. The emergency brake 200 of the second embodiment is a modification of the first emergency brake 100 that further includes a mechanical linkage 260 interconnecting the first and second eccentrics 210, 220. The mechanical linkage 260 includes first and second linkage bars 261, 262, each end of each linkage bar having an opening to receive a fastener 263 therein. The first and second eccentrics 210, 220 each have an opening to receive the fastener 263 to connect each linkage bar 261, 262 to each eccentric. The opening is located near one end of the edge 216 of each eccentric 210, 220. Using fasteners 263, the first linkage bar 261 is connected to the first eccentric 210 at one end and the second linkage bar 262 at the other end. The second linkage bar 262 is connected to the second eccentric 220 at one end and the first linkage bar 261 at the other end. The first and second linkage bars 261, 262 hang below the first and second eccentrics 210, 220. Each linkage bar 261, 262 is made from a single piece of metal, such as steel, or other suitable material. Fasteners 263 create a pin connection allowing the first and second linkage bars 261, 262 and first and second eccentrics 210, 220 to rotate independent of each other.

The mechanical linkage 260 provides additional mass to facilitate compression of the spring 240 by the first and second eccentrics 210, 220. Thus, when the emergency brakes 100 and 200 are generally similar in size, a stronger spring 240 may be used in the emergency brake 200 of the second embodiment than the emergency brake 100 of the first embodiment to compensate for the additional mass of the mechanical linkage 260. However, it is understood that the springs 140 and 240 are sized according to each emergency brake 100, 200. For example, where the emergency brake 200 has a smaller mass than emergency brake 100, the spring 240 may not be stronger than spring 140. In addition, the mechanical linkage 260 prevents the first and second eccentrics 210, 220 from over rotation when the emergency brake 200 is attached to the telescoping mast 40, when the first and second eccentrics are in the locked position, and when the emergency brake is not yet attached to the telescoping mast during assembly.

In the illustrated embodiment, an emergency brake 100 of the first embodiment is attached to the lower end of the inner mast section 42 and an emergency brake 200 of the second embodiment is attached to the lower end of the second inner mast section 43. It is appreciated that the emergency brake 100 and emergency brake 200 are interchangeable. For example, after accounting for the differences in relative size and placement, the emergency brake 200 can be attached to the inner mast section 42 and the emergency brake 100 can be attached to the second inner mast section 43, or the telescoping mast 40 can only include one type of emergency brake 100 or 200 for each mast section.

The emergency brake 200 of the second embodiment is secured to the second inner mast section 43 and operates in a similar way as described above in reference to emergency brake 100. The second inner mast section 43 includes first and second openings 71, 72 corresponding to the first and second eccentrics 210, 220. The first and second openings 71, 72 are positioned to allow the first and second eccentrics 210, 220 to rotate and extend through the first and second openings to engage the inner mast section 42. In the unlocked position, shown in FIG. 4, the first and second eccentrics 210, 220 are free of locking engagement with the inner mast section 42 and the second inner mast section 43 is free to retract within the inner mast section. Upon a sudden and uncontrollable descent, the first and second eccentrics 210, 220 move or rotate into a locked position, shown in FIG. 6, in which the first and second eccentrics are in locking engagement with the inner mast section to inhibit retraction of the second inner mast section within the inner mast section.

It is apparent that more than three mast sections can be included in the telescoping mast 40 and that any mast section telescopically received within another mast section can include an emergency brake 100 or 200 as described herein to prevent the mast section from falling relative to the other mast section. It is also apparent that while the brakes described above include first and second eccentrics 110, 120 or 210, 220, it is possible that the brakes only have one eccentric. In such an arrangement, one end of the spring 140 or 240 would remain attached to the eccentric and the other end would be secured to the shaft or elsewhere on the mast section.

Referring to FIGS. 1, 15 and 16, the head piece 80 is mounted on the telescoping mast 40 and supports a load thereon. In the illustrated embodiment, the head piece 80 is configured to support a panel. However, it is understood the head piece may have other configurations and can support other types of loads without departing from the scope of the present invention. The head piece 80 includes a mounting assembly 81 connected to a cross member 82. The cross member 82 extends on either side of the mounting assembly 81 in equal directions. A cross arm 83 is secured to each end of the cross member 82. Each cross arm 83 extends in a transverse direction to the longitudinal axis of the cross member 82. Thus, the cross arms 83 are generally parallel with respect to one another. The cross arms 83 extend on either side of the cross member 82. A hook 84 is placed at one end of each cross arm 83. As explained more below, the hooks 84 support the load or panel (not shown) when the panel is placed on the head piece 80. Hooks 84 can either be a rigid member attached to the end of each cross arm 83 as shown, or a spring loaded hook capable of rotating out of a loading position when necessary during lift use. Two panel edge supports 85 are positioned adjacent to each end of the cross member 82. In the illustrated embodiment, each panel edge support 85 is a short, rectangular bar oriented in a transverse direction to the longitudinal axis of the cross member. Thus, the panel edge supports 85 are generally parallel to the cross arms 83. The panel edge supports can have a covering 86, such as rubber end caps.

Each panel edge support 85 is secured to one end of a movable rail 87. Each rail 87 is a c-shaped channel and fits inside the hollow body of the cross member 82. The end of the rail 87 opposite the panel edge support 85 is positioned inside the hollow body of the cross member 82. Each rail 87 can slide in and out of an open end of the cross member 82. In this manner, each rail 87 slides along the cross member 82 on one side and the other rail 87 on the opposite side. Both rails 87 can slide pass each other as they slide inside the hollow body of the cross member 82. Adjacent to each open end of the cross member 82 is a locking pin 88. The locking pin 88 engages a set of holes (not shown) located on each rail 87 to prevent the rail from sliding. The holes are spaced at set intervals along the length of each rail 87. Each locking pin 88 is connected to the side of the cross member 82 corresponding to the side the rail 87 slides along. As the rail 87 slides in and out of the cross member 82, the locking pin 88 can engage a hole to prevent the rail from further movement. The locking pins 88 can be biased in a locked configuration with a spring. In this manner, the locking pins 88 can be pulled away from the cross member 82 to disengage the pin from the hole in the rail 87 and then snap back into another hole as the rail is sliding. As explained in more detail below, the ability for the panel edge supports 85 to be moved to different locations allows the head piece 80 to support different panels of varying widths.

Referring to FIG. 1, the mounting assembly 81 connects the cross member 82 to the telescoping mast 40. As seen in FIG. 16, the mounting assembly 81 includes a cross member bracket 89 and a mounting base 90. The cross member bracket 89 has a base 91 with two side flanges 92, each side flange extending from opposite edge margins of the base. The side flanges 92 are generally parallel with one another and perpendicular to the base 91. A back flange 93 extends from a back edge margin of the base 91 in the same direction as the side flanges 92. The back flange 93 spans between the two side flanges 92 and is secured to the cross member 82. The back flange 93 is generally perpendicular to the side flanges 92 and the base 91. Each side flange 92 has a vertical slot 94. As explained in more detail below, the slots 94 are aligned and shaped to allow a shaft 95 to slide along the length of each slot.

The mounting base 90 has opposite top and bottom surfaces. A pin 96 extends from the bottom surface in a direction away from the top surface of the mounting base 90. The pin 96 is sized and shaped to fit inside a corresponding cylindrical opening in the top of the telescoping mast 40. Two bearing flanges 97 extend from the top surface in a direction away from the bottom surface of the mounting base 90. The two bearing flanges 97 are generally parallel with one another. A bearing 98 is secured to each bearing flange 97. The bearings 98 are aligned and receive a shaft 95 therein. The shaft 95 is longer than the width of the mounting base 90 such that when the shaft is inserted into the bearings 98, each end of the shaft extends pass the side edge margin of the mounting base 90. A hole at the center of the shaft 95 receives a fastener 27 to connect a spring bracket 99 to the shaft. The spring bracket 99 is U-shaped with a hole on either side. The fastener 27 extends through the hole on one side of the spring bracket 99, through the hole in the shaft 95 and then through the opposite side of spring bracket to connect the spring bracket to the shaft. This connection allows the spring bracket 99 to pivot. A spring shaft 79 extends from the spring bracket 99 in an opposite direction from the sides of the spring bracket. A spiral spring 78 surrounds the spring shaft.

Referring to FIG. 16, the connection between the mounting base 90 and the cross member bracket 89 will now be described. As shown, the shaft 95 extends through both slots 94 in the cross member bracket 89. Any contact between the side flanges 92 and the bearings 98 prevents the cross member bracket 89 from falling off the shaft 95. The shaft 95 is secured in place with the fastener 27 and spring bracket 99. Because the spring bracket 99 is connected to the shaft 95 in between the bearings 98, any contact between the spring shaft and bearings prevents the shaft from sliding off the bearings. The base 91 of cross member bracket 89 has a hole 77 aligned with the slots 94. The spring shaft 79 extends through this hole 77. As a result, the spring 78 is compressed between the spring bracket 99 and the base 91 of the cross member bracket 89. The spring 78 pushes the cross member bracket 89 up until an end of the slot 94 contacts the shaft 95. This configuration securely locks the cross member bracket 89 to the mounting base 90 but still allows the cross member bracket to tilt and rotate relative to the mounting base. When the cross member bracket 89 is rotated by a user, the base 91 of the cross member bracket 89 applies force to the spring shaft 79, rotating the shaft 95 in the bearings 98. Thus, the cross member 82 and cross arms 83 can be rotated by the user. A spring loaded clip 76 can be attached to a rear edge of the mounting base 90 and extend along the back flange 93 of the cross member bracket 89. The spring loaded clip 76 can engage a protrusion in the back flange 93 to lock the cross arms 83 in a horizontal plane. Releasing the clip 76 allows the cross arms 83 to freely rotate. When a force is applied to the cross arms 83 or cross member 82, such as the loading of a panel on the head piece 80, the cross member bracket 89 can tilt from side to side. The applied force pushes the cross member bracket 89 down, sliding the shaft 95 along the length of the slot 94. The cross member bracket 89 can only tilt as far as the slot 94 allows. In other words, the cross member bracket 89 can only tilt until the shaft 95 contact the upper end of the slot 94. When the cross member bracket 89 tilts, the spring 78 is compressed even further between the base 91 of the cross member bracket 89 and the spring bracket 99. Once the force tilting the cross member bracket 89 is removed, the spring 78 pushes the cross member bracket 89 up until the shaft 95 contacts the lower end of each slot 94.

To load a panel onto the head piece 80, typically the cross arms 83 will be rotated to position the hooks 84 closer to the floor. The panel can also be loaded onto the head piece 80 when the clip 76 locks the cross arms 83 in a horizontal plane. In the illustrated embodiment, the cross arms 83 rotate until the base 91 of the cross member bracket 89 or the spring 78 contacts the mounting base 90. In the preferred embodiment, the cross arms 83 rotate a maximum of about 60 degrees relative to the horizontal plane. However, any rotation between 0 and 90 degrees is within the scope of the present invention. Once the cross arms 83 are rotated, the panel is placed on the cross arms with the hooks 84 engaging the lower edge of the panel to prevent the panel from sliding off. The rails 87 slide in or out of the cross member 82 to position the panel edge supports 85 adjacent to the sides of the panel. Each panel edge support 85 prevents the panel from sliding or tilting off the cross arms 83.

To attach the head piece 80 to the telescoping mast 40, the pin 96 is inserted into the corresponding cylindrical opening in the top of the telescoping mast. To remove the head piece 80, the head piece is lifted until the pin 96 is no longer in the cylindrical opening. The pin 96 also allows the head piece 80 to rotate, 360 degrees, around the telescoping mast 40 to better position the cross arms 83 and/or panel.

To operate the panel lift 10, the operator assembles the panel lift 10 by deploying the legs 25 on the base 20, inserting the lower end of the telescoping mast 40 into the mast holder 21, and inserting the pin 96 of the head piece 80 into the cylindrical opening at the upper end of the telescoping mast. The operator then adjusts the head piece 80 to receive the panel. Once the panel is loaded onto the head piece 80, the operator turns the winch 44 to retract the line 49 and extend the telescoping mast 40 in an upward direction. After the panel is unloaded, the operator turns the winch 44 in the opposite direction to extend the line 49 and retract the telescoping mast 40 in a downward direction. As the telescoping mast 40 retracts, the first and second eccentrics 110, 120 and 210, 220 of each brake remain in an unlocked position, free of locking engagement, allowing the inner mast section 42 to retract within the outer mast section 41 and the second inner mast section 43 to retract within the inner mast section 42. If the line or other flexible connection member 49 breaks while the telescoping mast 40 is in an extended position, the emergency brake 100 on the inner mast section 42 will engage the outer mast section 41, preventing the inner mast section from collapsing relative to the outer mast section. Likewise, the emergency brake 200 on the second inner mast section 43 will engage the inner mast section 42, preventing the second inner mast section from collapsing relative to the inner mast section. If the emergency brakes 100 and 200 engage, the operator can then disengage each brake and retract the telescoping mast 40. Once the operator is done using the panel lift 10, the operator can disassemble the panel lift by detaching the head piece 80, the telescoping mast 40, and the base 20 for each other.

In view of the above, it will be seen that the several features of the invention are achieved and other advantageous results obtained.

The telescoping structure 40 is removably secured to the base 20 in a manner to prevent horizontal movement or wiggle. The upper opening 34 is sized to tightly receive the telescoping mast 40 and the angled interior holder surfaces 37 are able to engage each side of the telescoping mast, as the telescoping mast is lowered into the base 20, to ensure the telescoping mast is firmly secured in the base. In another aspect of the present invention, the telescoping mast 40 does not rely on a braking system connected to the winch to prevent the telescoping mast from falling. The emergency brakes 100 and 200 of the present invention operate independent of any prime mover, such as a line 49, used to extend or retract the telescoping mast. Thus, the emergency brakes 100 and 200 can stop the sections of the telescoping mast 40 from collapsing in the event the prime mover fails.

Having described the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.

When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

As various changes could be made in the above products without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 

What is claimed is:
 1. A lifting device for elevating a load, the lifting device comprising: a telescoping mast having opposite upper and lower ends, the telescoping mast including an outer mast section and an inner mast section telescopically received within the outer mast section and configured to extend in an upward direction and retract in a downward direction relative to the outer mast section; and an emergency brake secured to the inner mast section, the emergency brake including first and second eccentrics configured to rotate relative to the inner mast section between an unlocked position, in which the first and second eccentrics are free from locking engagement with the outer mast section to allow retraction of the inner mast section within the outer mast section, and a locked position, in which the first and second eccentrics are in locking engagement with the outer mast section to inhibit retraction of the inner mast section within the outer mast section.
 2. The lifting device of claim 1, wherein the first and second eccentrics are configured to rotate to the locked position when the inner mast section accelerates relative to the outer mast section in the downward direction at a magnitude that is greater than a threshold magnitude.
 3. The lifting device of claim 2, wherein the eccentrics are configured to be free from engagement with the outer mast section to allow retraction of the telescoping mast when the when the inner mast section accelerates relative to the outer mast section in the downward direction at a magnitude that is less than a threshold magnitude.
 4. The lifting device of claim 1, wherein the emergency brake further includes a shaft attached to the inner mast section, the first and second eccentrics rotatably mounted on the shaft.
 5. The lifting device of claim 4, wherein the emergency shaft is attached inside the inner mast section.
 6. The lifting device of claim 5, wherein the inner mast section defines first and second openings, wherein the first eccentric is configured to extend through the first opening in the locked position, and the second eccentric is configured to extend through the second opening in the locked position.
 7. The lifting device of claim 1, wherein the emergency brake further includes a spring applying a spring force to the first and second eccentrics when the first and second eccentrics are in the unlocked position to facilitate rotation of the first and second eccentrics toward the locked position.
 8. The lifting device of claim 7, wherein the first and second eccentrics compress the spring when the first and second eccentrics are at rest relative to the inner mast section and in the unlocked position.
 9. The lifting device of claim 8, wherein the emergency brake further comprises a mechanical linkage interconnecting the first and second eccentrics, the linkage facilitating compression of the spring by the first and second eccentrics.
 10. The lifting device of claim 1, wherein the first and second eccentrics are configured to rotate in opposite directions from the unlocked position to the locked position.
 11. The lift of claim 1, wherein each of the first and second eccentrics includes a friction-enhancing structure configured to engage the outer mast section in the locked position.
 12. The lifting device of claim 1, wherein the telescoping mast further comprises: a second inner mast section telescopically received within the inner mast section and configured to extend in an upward direction and retract in a downward direction relative to the inner mast section; and a second emergency brake secured to the second inner mast section, the second emergency brake including first and second eccentrics configured to rotate relative to the second inner mast section between an unlocked position, in which the first and second eccentrics of the second emergency brake are free from locking engagement with the inner mast section to allow retraction of the second inner mast section within the inner mast section, and a locked position, in which the first and second eccentrics of the second emergency brake are in locking engagement with the inner mast section to inhibit retraction of the second inner mast section within the inner mast section.
 13. The lifting device of claim 11, wherein the inner mast section includes a stop positioned above the brake and configured to engage a lower end of the second inner mast section to inhibit the second inner mast section from contacting the emergency brake.
 14. The lifting device of claim 1, further comprising a prime mover operatively connected to the inner mast section and configured to extend the inner mast section in an upward direction and retract the inner mast section in a downward direction, wherein the emergency brake operates independent of the prime mover.
 15. The lifting device of claim 1, further comprising a base configured to support the telescoping mast in an upright position.
 16. The lifting device of claim 16, wherein the base includes a mast holder sized and shaped to receive a lower end of the telescoping mast therein, the mast holder defining an opening at an upper end thereof and through which the lower end of the telescoping mast enters the mast holder, wherein the mast holder includes opposing interior holder surfaces configured to engage the lower end of the telescoping mast when the telescoping mast is received in the mast holder, the opposing interior holder surfaces defining a transverse distance therebetween that tapers in a downward direction away from the opening.
 17. The lifting device of claim 1, further comprising a head piece secured to the telescoping mast and configured to support the load thereon.
 18. A lifting device for elevating a load, the lifting device comprising: a telescoping mast configured to extend and retract in a heightwise direction, the telescoping mast having opposite upper and lower ends; a head piece secured to the telescoping mast at the upper end thereof and configured to support the load thereon; and a base configured to support the telescoping mast in an upright position, the base including a mast holder sized and shaped to receive a lower end of the telescoping mast therein, the mast holder defining an opening at an upper end thereof and through which the lower end of the telescoping mast enters the mast holder, wherein the mast holder includes opposing interior mast holder surfaces configured to engage the lower end of the telescoping mast when the telescoping mast is received in the mast holder, the opposing interior holder surfaces defining a transverse distance therebetween that tapers in a downward direction away from the opening.
 19. The lifting device of claim 18, wherein the mast holder further includes second opposing interior holder surfaces configured to engage the lower end of the telescoping mast when the telescoping mast is received in the mast holder, the second opposing interior holder surfaces defining a transverse distance therebetween that tapers in the downward direction away from the opening.
 20. The lifting device of claim 18, wherein the telescoping mast is removably receivable in the mast holder. 